1. Technical Field
The present invention relates to a counter propeller propulsion unit for use in a relatively lightweight moving body such as a light plane, a motor hang glider, a motor paraglider, a paraplane, a Hovercraft, a lightweight helicopter and the like.
2. Background Art
For typical propeller propulsion aircraft, single row propellers arranged on a single rotational plane have heretofore been employed. The single row propeller produces torque by which the airframe tends to turn in a direction opposite to the direction in which the propeller rotates because of the reaction of the torque produced by the rotation of the propeller. So, counter propellers came onstage in order to stabilize the steering of the airframe by neutralizing the torque of the propellers.
As disclosed in JP-B-7-112834 and JP-A-8-156894, for example, gears have been used for conventional counter propellers in transmission mechanisms for transmitting rotating force of engines and propellers.
Such a counter propeller mechanism conventionally using gears has been developed for comparatively large-sized airframe and the mechanism is not only complicated in structure but also extremely heavy. Consequently, it has been difficult to use the counter propeller mechanism in any lightweight moving body mentioned above. Furthermore, because the gears are contained in a box, there exist problems arising from difficulties in troubleshooting and predicting trouble for ensuring safety, and inconvenience in view of doing maintenance.
An object of the present invention made to solve the foregoing problems is to provide a lightweight, highly safe counter propeller propulsion unit which is extremely simple in structure and particularly capable of securing stable steering when loaded in a lightweight moving body susceptible to an effect by a torque reaction. The propeller propulsion unit of the present invention is free from the use of a conventional gear actuating lubricant, as well as being easy to solely repair and replace parts for troubleshooting purposes. The propulsion unit also enables easy maintenance so as to predict any trouble.
In order to solve the foregoing problems, the counter propeller propulsion unit according to the invention comprises a prime mover, propellers, and a rotating force transmission means for transmitting the rotating force of the prime mover to the propellers, wherein a counter propeller is fixed to a main shaft and a forward propeller is pivoted rotatably on the main shaft, and these propellers are rotated in the directions reverse to each other by a belt transmission mechanism having forward and reverse running belts. The rotating force transmission means includes a power pulley secured to the driving shaft of the prime mover, a forward pulley secured to the forward propeller pivoted rotatably on the main shaft, a reverse pulley secured to the main shaft, a forward running belt for interlocking the reverse pulley with a tension pulley. The terms xe2x80x98forwardxe2x80x99 and xe2x80x98reversexe2x80x99 used in this description mean the relative relation of directions of rotation depending on the direction of rotation of the propeller.
To solve the foregoing problems, the counter propeller propulsion unit according to the invention is characterized in that in its rotating force transmission means, the belt transmission mechanism includes switching the power and tension pulleys, the forward running belt for interlocking the forward pulley with the tension pulley, the reverse running belt for interlocking the reverse pulley with the power pulley, and the belt transmission mechanism for interlocking one of the belts supported between both the pulleys of the reverse running belt with the tension pulley from the outside whereby to rotate the propellers in the directions reverse to each other.
To solve the foregoing problems, it is preferred for the counter propeller propulsion unit according to the invention to have the face of the forward and/or reverse running belt in contact with at least each pulley having a plurality of substantially inverted-V ribs in the longer direction and for the surface of the pulley in contact with the belt to have substantially sectionally V-shaped grooves engaging with the respective ribs in the circumferential direction.
To solve the foregoing problems, moreover, the counter propeller propulsion unit according to the invention is characterized in that in its rotating force transmission means, chains in place of belts, and sprockets in place of pulleys are used in a chain transmission mechanism for rotating propellers in the directions reverse to each other.
Although the belt transmission mechanism is mainly described by way of example in the following specification, the belt and the pulley will be understood to mean a chain and a sprocket respectively unless otherwise specified.
In the counter propeller propulsion unit according to the invention, two belts (the forward and reverse running belts) or two chains and corresponding pulleys or sprockets are so structured as to be used to transmit the rotating force of the prime mover to the propellers.
According to a first aspect of the invention, the rotating force produced by the prime mover is transmitted via the forward running belt from the power pulley secured to the driving shaft. Then the forward propeller secured to the forward pulley is rotated in the same direction of rotation of the driving shaft.
On the other hand, the rotating force is transmitted to the reverse pulley as the power pulley secured to the driving shaft is interlocked with the outer side of the reverse running belt and then transmitted to the counter propeller from the reverse pulley via the main shaft, so that the counter propeller is rotated in the direction opposite to that of the driving shaft.
According to a second aspect of the invention, the rotating force produced by the prime mover is transmitted from the power pulley secured to the driving shaft via the reverse running belt to the reverse pulley. The rotating force is then transmitted to the forward pulley via the forward running belt, thus causing the forward propeller secured to the forward pulley to rotate in the direction opposite to the direction of rotating the driving shaft. Further, the rotating force of the reverse pulley is transmitted via the main shaft to the counter propeller so as to rotate the counter propeller in the same direction as that of the driving shaft.
As stated above, two rows of propellers having a common axis are rotated in the directions reverse to each other while canceling a defect due to the synchronous property of the single row propeller, that is, canceling counter torque causing the moving body to make a roll in one direction and moreover the gyro-effect of bringing about deflection from its progressing direction is neutralized; this results in decreasing the swinging of the aircraft on one side when it takes off. Even when a sudden increase or decrease in the engine output occurs, the aircraft operability still remains improvable without any Dutch roll.
Further, a belt is normally subjected to elastic deformation because of the difference in tension between its stretching and loosening sides and a change in its length functions as what is a so-called belt creep phenomenon in which the belt appears to slip on the surface of a pulley and this results in minimizing the load applied to an engine at the time it is started or suddenly accelerated, also making the engine easy to start or accelerate or preventing it from undergoing fatigue.
With the ribs on the surface of the belt that is brought into contact with the pulley and those to be mated with the respective grooves formed therein, the contact area therebetween is far greater than what is obtainable from a simple planar contact to ensure that the rotating force of the prime mover is transmitted to the propellers. In other words, the belts are prevented from laterally moving and also from being brought into contact with each other.